The present invention relates to diversity antennas generally and to polarization diversity antennas in particular.
Diversity antennas are used to exploit the random nature of radio wave propagation by finding significantly uncorrelated signal paths for wireless communication. They are of particular use in mobile wireless communication which requires that the signal be transmitted with high quality. Space and pattern diversity are very popular in land-mobile communication but require large mounting space to obtain high diversity efficiency.
Indoor wireless networks require less space for antennas. One example is a notch-wire antenna described in the article xe2x80x9cA Notch-Wire Composite Antenna for Polarization Diversity Receptionxe2x80x9d by Kuga et al., IEEE Transactions on Antennas and Proragation, Vol. 46, No. 6, June 1998, pp. 902-905, and in U.S. Pat. No. 5,402,136, both of which are incorporated herein by reference. This antenna provides polarization diversity reception in an indoor wireless system. The antenna is formed of two antennas, a disk antenna having three notches therein and a wire-loop antenna.
Other notch antennas are described in U.S. Pat. No. 5,591,401.
Unfortunately, these antennas require coaxial cables to connect them to the system that processes the received signal. Usually, the system is implemented in a printed circuit board to which it is not easy to connect a coaxial cable. To do so requires a special adapter that provides a smooth transition of the characteristic impedance, from the impedance of the coaxial line to the impedance of the electronics of the printed circuit board. Furthermore, connecting a coaxial cable to the elements of the antenna requires welding or soldering. Both are costly and time-consuming processes.
Moreover, the printed circuit board forms a ground plane that interferes with the horizontally polarized antenna of the polarization pair. Once connected to the printed circuit board, the radiation pattern performance of the horizontally polarized antenna deteriorates. This degrades the advantage of the polarization diversity.
An object of the present invention is to provide an antenna that is connected to a printed circuit board via a coaxial connector.
A further object of the present invention is to provide a coaxial connector that is relatively easy to manufacture.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a diversity polarization antenna for connecting to a printed circuit board. The antenna includes a horizontally polarized antenna, a vertically polarized antenna whose phase center coincides with the phase center of the horizontally polarized antenna and a fixed height coaxial connector. The connector connects the antennas to the printed circuit board and has a height such that the deviation of the radiation pattern of the horizontally polarized antenna from omnidirectionality is within xc2x16 dB.
Additionally, in accordance with a preferred embodiment of the present invention, the connector includes two metal tubes of the fixed height, two insulating tubes locatable in one of the two metal tubes and an eyelet connector. The insulating tubes have a diameter which is slightly wider than the outer diameter of a metal wire. The eyelet connector has two short toothed tubes which receive the metal tubes and have a diameter which is generally the same as the outer diameter of the metal tubes. The eyelet connector also has at least two pins for connecting into the printed circuit board.
Moreover, in accordance with a preferred embodiment of the present invention, the two metal tubes are formed into a double tube unit
Alternatively, in accordance with a preferred embodiment of the present invention, the antenna includes a radiating wire for a vertically polarized antenna, a feeding wire for a horizontally polarized antenna metal disk with notches and a fixed height coaxial connector. The metal disk forms part of the vertically polarized antenna and the notches form part of the horizontally polarized antenna. The connector physically and electrically connects the wires and the metal disk to the printed circuit board.
Further, in accordance with a preferred embodiment of the present invention, the metal disk has two short, toothed tubes, the center of one of which coincides with the center of the metal disk.
Still further, in accordance with a preferred embodiment of the present invention, the connector includes two metal tubes locatable within the toothed tubes of the metal disk, two insulating tubes, which receive and insulate the feeding and radiating wires and an eyelet connector. Each insulating tube is locatable in one of the two metal tubes. The eyelet connector has two short toothed tubes that receive the metal tubes and at least two pins, which connect into the printed circuit board. The toothed tubes have a diameter, which is generally the same as the outer diameter of the metal tubes.
Moreover, in accordance with a preferred embodiment of the present invention, the antenna also includes a support disk to which the metal disk and the wires are attachable.
Further, in accordance with a preferred embodiment of the present invention, the radiating wire has arms, the metal disk is attachable to an undersurface of the support disk and the support disk has supports for the arms which hold the arnms at a distance L above an upper surface of the support disk.
There is also provided, in accordance with a preferred embodiment of the present invention, an antenna which connects to a printed circuit board and which includes a horizontally polarized antenna and a fixed height coaxial connector such as is described hereinabove.
Moreover, in accordance with a preferred embodiment of the present invention, the coaxial connector can have one or two sections for connecting one or two antennas.
The present invention incorporates the antenna, the coaxial connector and the eyelet connector individually and in combination.
There is also provided, in accordance with a preferred embodiment of the present invention, a method of manufacturing a double tube outer connector of a coaxial connector. The method includes the steps of providing a rectangular metal sheet having two long and two short edges with cutouts at the center of its long edges and rolling each of the two short edges toward the center, thereby to form two double tubes.
Finally, there is further provided, in accordance with a preferred embodiment of the present invention, a method of connecting at least a horizontally polarized antenna to a printed circuit board. The method includes the steps of connecting the antenna to a fixed height coaxial connector, the height of the connector being such that that the deviation of the radiation pattern of the horizontally polarized antenna from omnidirectionality is within xc2x16 dB and connecting the connector to the printed circuit board.